1. Technical Field
The embodiments herein generally relate to gain control circuits, and, more particularly, to circuits used for improving the dynamic range with low noise figure at sensitivity and improve step gain in communication devices.
2. Description of the Related Art
As shown in FIG. 1, the tuner input goes to both a low noise amplifier (LNA) input and an attenuator input creating two separate signal paths (both paths have variable gain control). However, the gain control is continuous as in a baseband variable gain amplifier (VGA), which comes at the expense of inferior linearity at high signal levels. Moreover, fine stepping the gain allows for easier and smarter logic processing deciding how to step the front end gain.
Conventionally, the attenuators have taken the form of R-2R ladders as shown in FIG. 2, which typically require switches both in series with the signal path as well as in a shunt configuration. Furthermore, matching requirements at the input often constrain the values of these resistors to be quite small. The repercussions are large transistor switches, which tend to dramatically limit the bandwidth of the circuit. Accordingly, there remains a need for a highly linear, low noise figure front end circuit that can provide fine step gain control.